Featured Research

from universities, journals, and other organizations

Galaxy merger dilemma solved

Date:

April 25, 2010

Source:

Naval Research Laboratory

Summary:

Scientists have solved a long-standing dilemma about the mass of infrared bright merging galaxies. Because galaxies are the largest directly observable objects in the universe, learning more about their formation is key to understanding how the universe works.

Share This

Optical (left) and Infrared (right) image of an IR-bright merging galaxy. The center of the merger is obscured in the left image, but in the infrared (right) the central disk is very bright and easily seen.

Credit: Optical image from the Hubble Space Telescope and infrared image from the University of Hawaii 88" telescope

Scientists at the Naval Research Laboratory have solved a long-standing dilemma about the mass of infrared bright merging galaxies. Because galaxies are the largest directly observable objects in the universe, learning more about their formation is key to understanding how the universe works.

Related Articles

Dr. Barry Rothberg and Dr. Jacqueline Fischer, both of the Infrared-Submillimeter Astrophysics & Techniques Section in the Remote Sensing Division, used new data from the 8-meter Gemini-South telescope in Chile along with earlier results from the W. M. Keck-2 10-meter and University of Hawaii 2.2-meter telescopes in Hawaii and archival data from the Hubble Space Telescope, to solve the problem. They have published a paper on their research findings on galaxy evolution in the Astrophysical Journal.

Galaxies in the Universe generally come in two shapes, spiral, like our own Milky Way, and elliptical, in which the stars move in random orbits, Rothberg explains. The largest galaxies in the Universe are elliptical in shape and how they formed is central to our understanding how the Universe has evolved over the last 15 billion years. The long-standing theory has been that spiral galaxies merge with each other forming most of the elliptical galaxies in the Universe. Spiral galaxies contain significant amounts of cold hydrogen gas. When they merge, the beautiful spiral patterns are destroyed and the gas is converted into new stars. The more gas present in the spiral galaxies, the more stars are formed and with it, large amounts of dust. The dust is heated by the young stars and radiates energy at infrared wavelengths.

Until recently scientists thought that these infrared bright merging galaxies were not massive enough to be the precursors of most elliptical galaxies in the Universe. The problem lay in the method of measuring their mass. The conventional method of measuring mass in dusty IR-bright galaxies uses near-infrared light to measure the random motions of old-stars. The larger the random motions, the more mass is present. Using near-infrared light makes it possible to penetrate the dust and see as many of the old stars as possible.

However, a complication occurs when spiral galaxies merge, because most of their gas is funneled to the gravitational center of the system and forms a rotating disk. This rotating disk of gas is transformed into a rotating disk of young stars that is also very bright at near-infrared wavelengths. The rotating disk of young stars both outshines the old stars and makes it appear as if the old stars have significantly less random motion. In contrast to this conventional method, Rothberg and Fischer instead observed the random motions of old stars at shorter wavelengths effectively using the dust to their advantage to block the light from the young stars. Their new results showed that the old stars in merging galaxies have large random motions, which means they will eventually become very massive elliptical galaxies.

The next step for NRL researches is to directly observe the stellar disks in IR luminous mergers using three-dimensional spectroscopy. Each pixel is a spectrum, and from this the researchers can make two-dimensional maps of stellar motion and stellar age. This will allow them to measure the size, rotation, luminosity, mass and age of the central disk.

More From ScienceDaily

More Space & Time News

Featured Research

Mar. 3, 2015 — Like the lost little puppy that wanders too far from home, astronomers have found an unusually small and distant group of stars that seems oddly out of place. The cluster, made of only a handful of ... full story

Mar. 3, 2015 — Meteorologists sometimes struggle to accurately predict the weather here on Earth, but now we can find out how cloudy it is on planets outside our solar system, thanks to new ... full story

Mar. 3, 2015 — Recent research contributes to the effort to determine the nature of dark matter, one of the most important mysteries in physics. As indirect evidence provided by its gravitational effects, dark ... full story

Mar. 2, 2015 — Dust plays an extremely important role in the universe -- both in the formation of planets and new stars. But the earliest galaxies had no dust, only gas. Now an international team of astronomers has ... full story

Mar. 2, 2015 — NASA's Dawn spacecraft has returned new images captured on approach to its historic orbit insertion at the dwarf planet Ceres. Dawn will be the first mission to successfully visit a dwarf planet when ... full story

Mar. 2, 2015 — An international team of researchers has demonstrated a way to assess the quality of water on Earth from space by using satellite technology that can visualize pollution levels otherwise invisible to ... full story

Feb. 27, 2015 — A new type of methane-based, oxygen-free life form that can metabolize and reproduce similar to life on Earth has been modeled. It is theorized to have a cell membrane, composed of small organic ... full story

Feb. 27, 2015 — Astronomers using data from NASA's Wide-field Infrared Survey Explorer, or WISE, have found a cluster of stars forming at the very edge of our Milky Way galaxy. This is the first time astronomers ... full story

Feb. 26, 2015 — If you put a camera in the ice machine and watched water turn into ice, the process would look simple. But the mechanism behind liquids turning to solids is actually quite complex, and understanding ... full story

NASA EDGE: SMAP Launch

NASA (Mar. 2, 2015) — Join NASA EDGE as they cover the launch of the Soil Moisture Active Passive (SMAP) spacecraft live from Vandenberg Air Force Base. Special guests include NASA Administrator Charlie Bolden, SMAP Project System Engineer Shawn Goodman and Lt Col Brande Walton and Joseph Sims from the Air Force. No word on the Co-Host&apos;s whereabouts.
Video provided by NASA

Related Stories

Feb. 23, 2014 — The Andromeda Galaxy is surrounded by a swarm of small satellite galaxies. Researchers have detected a stream of stars in one of the Andromeda Galaxy's outer satellite galaxies, a dwarf galaxy ... full story

Feb. 23, 2014 — The dominating figure in the middle of this new Hubble image is a galaxy known as MCG-03-04-014. It belongs to a class of galaxies called luminous infrared galaxies -- galaxies that are incredibly ... full story

May 12, 2013 — When we look into the distant cosmos, the great majority of the objects we see are galaxies: immense gatherings of stars, planets, gas, dust, and dark matter, showing up in all kind of shapes. A new ... full story

Feb. 5, 2013 — The further away you look, the further back in time you see. Astronomers use this fact to study the evolution of the Universe by looking at nearby and more distant galaxies and comparing their ... full story

ScienceDaily features breaking news and videos about the latest discoveries in health, technology, the environment, and more -- from major news services and leading universities, scientific journals, and research organizations.